Fluid displacement apparatus of the scroll type typically include two parallel plates, eachhaving an involute wrap element disposed on one side. These involute elements, having offset and parallel axes, intermesh with each other such that the sides of the involutes and the parallel plates define sealed fluid pockets.
As one involute orbits the other, the fluid pockets move from an inlet port, along the flank surfaces of the involute wrap elements, and through an outlet port. Depending on the configuration of the involutes and their direction of orbital rotation, the volume of these moving pockets will either increase, decrease, or remain relatively constant. Thus, a scroll machine may function as an expander (vacuum pump), a compressor, or a liquid pump, respectively.
If one involute element were free to rotate with respect to the other, some of the fluid pocket seals would leak and the intermeshed involutes would bind together.Therefore, to prevent this it is necessary to have an anti-rotation coupling that maintains a fixed angular relationship between the involutes yet still allows one to orbit the other.
Designs for such couplings are well known in the prior art. For example, U.S. Pat. No. 3,924,977 discloses a conventional "Oldham coupling" comprising an annular ring with four sliding keys disposed at 90.degree. intervals around its perimeter. Two of the keys, at opposite sides of the ring engae slots in the orbiting element while the other two engage slots in the stationary portion of the machine. Although this coupling is effective, its bulk requires substantial space within the scroll machine and it is somewhat costly to manufacture.
Therefore, it is an object of this invention to provide a simple anti-rotation coupling that requires minimal space in a scroll machine.
It is a further object to provide an anti-rotation coupling that is less expensive to manufacture than conventional coupling designs.
It is yet a further object of this invention to produce an anti-rotaton coupling from an integral sheet metal stamping.
These and other objects will be apparent from the attached drawngs and the description of the preferred embodiments that follow below.